This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present invention. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present invention. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of any prior art.
A number of substances of commercial significance may be produced from natural sources, including biomass. Cellulosic biomass may be particularly advantageous in this regard due to the versatility of the abundant carbohydrates found therein in various forms. As used herein, the term “cellulosic biomass” refers to a living or formerly living biological material that contains cellulose. The lignocellulosic material found in the cell walls of higher plants is the world's largest source of carbohydrates. Materials commonly produced from cellulosic biomass may include, for example, paper and pulpwood via partial digestion, biofuels, including bioethanol by fermentation.
Development of fossil fuel alternatives derived from renewable resources have received recent attention. Cellulosic biomass has garnered particular attention in this regard due to its abundance and the versatility of the various constituents found therein, particularly cellulose and other carbohydrates. Despite promise and intense interest, the development and implementation of bio-based fuel technology has been slow. Existing technologies have heretofore produced fuels having a low energy density (e.g., bioethanol) and/or that are not fully compatible with existing engine designs and transportation infrastructure (e.g., methanol, biodiesel, Fischer-Tropsch diesel, hydrogen, and methane). Moreover, conventional bio-based processes have typically produced intermediates in dilute aqueous solutions (>50% water by weight) that are difficult to further process. Energy- and cost-efficient processes for processing cellulosic biomass into fuel blends having similar compositions to fossil fuels would be highly desirable to address the foregoing issues and others.
When converting cellulosic biomass into fuel blends and other materials, cellulose and other complex carbohydrates therein can be extracted and transformed into simpler organic molecules, which can be further processed thereafter. Subsequent transforming reactions include various hydrocatalytic reactions, such as hydrogenation and/or hydrogenolysis reactions, which require hydrogen. While external hydrogen can be provided, such a hydrogen source may not help reduce the carbon footprint of any eventual fuel product, such as when it is based on natural gas reforming.
Further, in addition to the desired carbohydrates, other substances may be present within cellulosic biomass that can be especially problematic to deal with in an energy- and cost-efficient manner. For example, during cellulosic biomass processing, the significant quantities of lignin present in cellulosic biomass may lead to fouling of processing equipment, potentially leading to costly system down time. The significant lignin quantities can also lead to realization of a relatively low conversion of the cellulosic biomass into useable substances per unit weight of feedstock.
As evidenced by the foregoing, the efficient conversion of cellulosic biomass into fuel blends and other materials is a complex problem that presents immense engineering challenges. The present disclosure addresses these challenges and provides related advantages as well.